A validating resolver is a DNS resolver that checks DNSSEC signatures to confirm that DNS answers are authentic and have not been altered. It follows the DNSSEC chain of trust from a configured trust anchor, typically the root, before returning an answer.
This helps defend against forged or tampered DNS responses, but validation depends on the resolver having current trust-anchor data. During a planned key rollover, a resolver that misses the replacement key may reject valid answers, causing lookup errors or application failures. Administrators should identify which resolvers perform validation, keep trust-anchor updates enabled, and monitor DNS logs for validation failures.